Jesus is co-eternal God. He assumed a human form, but was always God. This is just not what Mormons believe.
Suggest you read Frank Sheed's "Theology and Sanity" for a great discussion of the Trinity.
Am only saying. . .one has to think 'twice' and perhaps, beyond the words to the ideas that lie behind them. In that 'frame'; there remain similarities of thought; expressed a bit differently perhaps; between the idea of God/Man/Son. . .'created' etc.
The implications of the Trinity, notwithstanding; while we are not God; all of Creation, IS OF God (mind/body/spirit) as life unfolds from the One. . .'first' and in, and from the 'beginning'. That includes the Angels and Archangels (and Jesus as man if you will/and so believe) of which Lucifer was one - per story - and his fall precips, of course, that of Adam and Eve. Must have; after all; there was that snake in the Garden - repping 'evil' and/or knowledge; at least it's danger/threat.
Anyway; in this respect; evil is brother in that family; albeit, a wayward one, to Good. That 'brother' tells us evil is a part of our Creation family. If it were not; evil would not be recognizeable, no matter what form it took. (The very word, recognition; presumes a prior knowledge and so it is; we 're'cognize - re-know - that which we already know).
Evil at it's most horrific; always seems UNrecognizeable - words can fail us by description. . .until, we look further; and see - recognize a thread of humanity at work - albeit at it's worst.
Evil is not 'easily' recognized of course. It is not so easily ID as is the 'creature Devil', we have come to think of as Evil, personified, in a manner of speaking. He is almost a comedic figure, compared to genuine Evil at work in the world. And why, of course, real Evil so easily hides itself, by comparison. And of course, the Angels themselves were God's first works of innocence and art; so why would we not be so easily fooled.
Of course in all of this, remains a 'good' gone bad (a brother; gone wrong); but that evil-once-good; inhabits our world. It is, however, inferior to the Good; it once was. . (Interesting that Libs seem not to notice their inferiority but they survive, by depending on lies 'foretelling a good'; of course.) Evil; having given up 'good' must depend on the 'goodness' of others for it to get around and so again; reveals it's inferiority. Evil needs a good horse to ride. . .
Good,of course, does not need evil. Good will prevail eternally; and evil, will not...cannot.
Oh, too much; I digress; and I Thank You, for the book recommendation.
(In a way; Jesus served some of the same purpose;i.e.; giving God a 'face' so that mankind could 're-cognize' and remember, that from which we came. And realize ultimately, the purpose of Creation.)
And perhaps, by that MO; we can remember, on just what plane, Evil once resided; and how/why now; Evil exists as mankind's evil brother. And by that regard; was/is. . .at least, Jesus the 'man's' brother; albeit, not Jesus the Christ.
Anyway; not a Mormon; but do not hold it against them; what seems an irrational interpretation; given the rationality and irrationality of things believed by Faith alone.
And now. . .if you got this far; you can scream/sigh/lol. . if you have not already. . .